DOF And The 45 mm

For an 8"x10" print/display size viewed at the standard 25cm viewing-distance (which is what on-line DOF calculators assume), a COC diameter of 15 Microns is assumed for a M43 image-sensor such as the E-M5's (30 Microns for Full Frame divided by the M43 Crop Factor of 2.0).

A smaller COC diamter could be used (as small as 7.5 Microns, which is equal to the height/width of a 2x2 array of the E-M5's approximately 3.75 Micron sized photo-sites). The effect of choosing that (7.5 Micron COC diameter) is to halve the DOF and double the Hyperfocal Distance. This online-DO calculator is the only one that I know which allows the COC diameter to be specified by the user with a sufficiently high degree of numerical precision:

http://www.tawbaware.com/maxlyons/calc.htm

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You can closely approximate the DOF yourself using the formulas below. We presume that you are not shooting close-up/macro, and that the Camera to Subject Distance is a small fraction of the Hyperfocal Distance (less than around 33% for less than 11% error) when using a 45mm FL lens.

Distances in units of Meters:

DOF = (2) x (F) x (C) x ( D / L )^(2)

Distances in units of Feet:

DOF = (0.6096) x (F) x (C) x ( D / L )^(2)

where:

DOF is Depth of Field (in the distance units indicated above);

F is F-Number;

C is Circle of Confusion diameter (in units of Microns);

D is Camera to Subject Distance (in the distance units indicated above);

L is (actual) lens-system Focal Length when focused at infinity (in units of milliMeters).

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In all cases above:

To adjust for a different print/display size (other than 8"x10"), scale the Circle of Confusion Diameter (C) in inverse proportion to the amount of image-enlargement. Note that the minimum Circle of Confusion Diameter (C) is 7.5 Microns for the E-M5's image-sensor. That fact places an upper limit on the print/display size.

To adjust for a viewing-size (other than 25cm), scale the Circle of Confusion Diameter (C) in direct proportion to changes in the viewing-distance.